Until now, an image forming apparatus is well known, on which a developing device is installed for performing a development process by using developer such as toner and the like (For example, it may refer to the following Patent Document 1).    Patent Document 1: Japan patent publication of No. Heisei 2000-238374.
In such developing device, in order to supply the developer, there is a case to establish and use an exchangeable accommodating section of cartridge type.
FIG. 13 is a diagram showing a structure of a former developing device.
As shown by FIG. 13, a developing device 90 comprises a developing section 91 for forming electrostatic latent image; a supplying section 92 for supplying developer to the developing section 91; and an accommodating section 93 which is exchangeably installed on the supplying section 92 and accommodates the developer.
The developing section 91, as shown by FIG. 13, comprises a photosensitive drum 94 which as an image carrying body. Moreover, around the photosensitive drum 94, a charging roller 95 which uniformly charges the surface of the photosensitive drum 94; an exposing unit 96 used for exposing the surface of charged photosensitive drum 94 and forming electrostatic latent image; and a developing roller 97 used for making the developer adhere to the electrostatic latent image and forming a developer image on the surface of the photosensitive drum 94, are respectively arranged.
In the supplying section 92, as shown by FIG. 13, a supplying roller 98 that is used for supplying developer for the developing roller 97, and a developing blade 99 that is used for forming uniform developer layer the developing roller 97, are connected with and arranged on the surface of the developing roller 97. Moreover, in the supplying section 92, a detecting section 100 used for detecting reduction of supplied and consumed developer from the accommodating section 93 is established.
However, in the former developing device 90 above mentioned, because the detecting section 100 is installed under installation position of the accommodating section 93, after the accommodating section 93 became empty and a long time passed, the reduction of the developer is detected. Then, the developing device 90 requires user to exchange the accommodating section 93. Therefore, even if the accommodating section 93 becomes empty, there is also a problem that the user can not immediately grasp such state.
For solving the problem above mentioned, a way to set the detecting section 100 beside the installation position of the accommodating section 93 is considered, but also there are problems about cost and so on.
Therefore, when the developer in the accommodating section is exhausted, an image forming apparatus capable of informing user of the state is expected without changing the position of the detecting section.